Method and apparatus for reuse of abrasive fluid used in the manufacture of semiconductors

ABSTRACT

An apparatus and method recycles the abrasive fluid or slurry effluent used in the polishing step in the manufacture of semiconductors. Agglomerations of abrasive grains built up in the slurry effluent are crushed using a mill, ultrasonic oscillation, or pressurized circulation. The slurry effluent is then regenerated and reused.

BACKGROUND OF THE INVENTION

The invention relates to an apparatus for use in the manufacture ofsemiconductors, and more particularly, to a method and an apparatus forreuse of an abrasive fluid used in the manufacture of semiconductordevices.

A chemical-mechanical polishing (CMP) device is used in flattening awafer surface in a semiconductor manufacturing step. The CMP deviceemploys an abrasive slurry, and accordingly, as the quantity of productsmanufactured increases, the quantity of used abrasive slurry alsoincreases. The quantity of abrasive slurry used influences themanufacturing cost, and hence an efficient reuse of the used abrasiveslurry or fluid is required.

In the conventional practice of flattening a wafer surface, an abrasiveslurry in liquid form which comprises a commercially available abrasivestock having a weight percentage of approximately 25 wt % and diluted bydeionized water to nearly 13 wt % is used. Used abrasive fluid isfurther diluted within the polishing device to produce an effluent whichmay have a concentration on the order of about 0.1 to 0.2 wt %, forexample. It will be understood that the abrasive effluent containsfragments of films abraded from the wafer and impurities produced by apolishing table (or pad) of the polishing device. Abrasive effluents aregenerally passed through a neutralization treatment before disposal ordelivered to an industrial waste disposal undertaker in the form ofsludges which result from a drainage treatment. The abrasive fluidrepresents a significant proportion of the wafer processing cost, butthe abrasive effluent has been disposed of without a reuse thereof.

Abrasive grains contained in the abrasive effluent are agglomerated tolarger sizes. However, a single grain in the agglomeration has a graindiameter which remains substantially unchanged from the grain size whichit exhibited before it was fed to the polishing step, and thus retains agrain size which is still useable in the abrasive operation.Nevertheless, the grain agglomerations are disposed of without beingrecycled.

The cost of disposing sludges delivered to the industrial waste disposalundertaker adds to the semiconductor manufacturing cost. Thus, reuse ofthe abrasive effluent is of importance in reducing the semiconductormanufacturing cost.

It is an object of the invention to provide a method and an apparatuswhich allow reuse of an abrasive effluent.

SUMMARY OF THE INVENTION

In a first aspect of the present invention, a method is provided thatreuses a slurry effluent containing agglomerations of abrasive grainswhich has been used in a polishing step in the manufacture of asemiconductor. First, the agglomerations of abrasive grains contained inthe slurry effluent are crushed. Then, an abrasive fluid is regeneratedusing the slurry effluent containing the crushed abrasive grains.

In a second aspect of the present invention, an apparatus is providedthat reuses a slurry effluent containing agglomerations of abrasivegrains which has been used in a polishing step in the manufacture of asemiconductor. The apparatus includes a crusher for crushing theagglomerations of abrasive grains contained in the slurry effluent and aregeneration unit for regenerating an abrasive fluid using the slurryeffluent containing the crushed abrasive grains.

In a third aspect of the present invention, a crusher is provided thatcrushes agglomerations of abrasive grains contained in a slurry effluentwhich has been used in the manufacture of a semiconductor. The crusherincludes a tank for storing the slurry effluent and at least one of amill, an ultrasonic oscillator and a pressurizing circulation unitattached to the tank.

In a fourth aspect of the present invention, an apparatus forconcentrating a slurry effluent is provided. The apparatus includes aconcentrating unit including a concentrating membrane for separating theslurry effluent into a concentrate fluid and a permeate fluid; atemperature regulator for adjusting the temperature of the slurryeffluent; and a concentration controller for controlling the temperatureregulator to control the concentration of the concentrate fluid.

In a fifth aspect of the present invention, an apparatus for regulatingthe quality of a slurry effluent including abrasive grains is provided.The apparatus includes a tank for storing the slurry effluent and aspecific gravity adjusting unit for adjusting the concentration of theabrasive grains in the slurry effluent.

In a sixth aspect of the present invention, an apparatus for regulatingthe quality of a slurry effluent including abrasive grains is provided.The apparatus includes a tank for storing the slurry effluent and a pHadjusting unit for adjusting the pH of the slurry effluent.

In a seventh aspect of the present invention, an apparatus for cleansinga concentrating membrane used in concentrating a slurry effluent isprovided. A concentrate fluid and a permeate fluid are generated byconcentrating the slurry effluent. The apparatus includes a chamber fortemporarily storing the permeate fluid and a back washing unit forcleansing the concentrating membrane using the permeate fluid stored inthe chamber.

Other aspects and advantages of the invention will become apparent fromthe following description, taken in conjunction with the accompanyingdrawings, illustrating by way of example the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

FIG. 1 is a schematic diagram of an abrasive effluent regeneration plantaccording to one embodiment of the present invention;

FIG. 2 is a schematic diagram of a slurry effluent regeneration unit ofthe plant of FIG. 1; and

FIG. 3 is a schematic diagram of a crusher of the plant of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An abrasive effluent regeneration plant according to one embodiment ofthe present invention will now be described with reference to FIGS. 1 to3.

FIG. 1 is a schematic diagram of the abrasive effluent regenerationplant 1, which includes a circulation system including a feed system forfeeding an abrasive solution to a plurality of polishing devices 2,which may be three in number, and a regeneration system whichregenerates an abrasive effluent or a slurry effluent discharged fromthe polishing devices 2. Specifically, the plant 1 comprises a stocksolution drum cabinet 4 containing a stock solution drum 3, a slurryfeeder 5, and a slurry effluent regeneration unit 6. The polishingdevices 2 preferably comprise a chemical-mechanical polishing (CMP)device, which is used to abrade a metal layer or oxide layer ofaluminium, for example, formed on a semiconductor wafer.

The stock solution drum 3 contains a stock solution containing abrasivegrains, for example, fine particles of alumina. Preferably, the stocksolution has a concentration of about 25 wt %. The stock solution drum 3is connected to the slurry feeder 5 via a channel 7, and is alsoconnected to the slurry effluent regeneration unit 6 via a channel 8.The stock solution is fed to the feeder 5 and the unit 6 by openingvalves 9, 10 which are disposed in the channels 7,8, respectively.

While not shown, the slurry feeder 5 includes a mixing tank. A givenproportion of stock solution which is fed from the drum 3 is diluted byand mixed with deionized water (DIW) to prepare a slurry fluid. At thisend, deionized water used for the dilution is fed to the slurry feeder5. Preferably, the prepared slurry fluid has a concentration of about 13wt %. It is preferred that a pair of mixing tanks are provided to beused in an alternate fashion. The slurry feeder 5 is connected to eachof the polishing devices 2 via a feed channel 11, and a valve 12 isprovided in the feed channel 11 to allow the slurry fluid from theslurry feeder 5 to be fed to each of the polishing devices 2 when it isopened. The quantity of the slurry fluid fed to each polishing device 2is regulated by the opening of the valve 12.

Each polishing device 2 feeds the slurry fluid onto a polishing paddisposed on a rotary table, and polishes a wafer by urging the waferagainst the pad. Used slurry fluid is diluted by water and is thendischarged as a slurry effluent, thus preventing loading or plugging ofa clearance around the table by abrasive grains. The slurry effluent hasa concentration of preferably about 0.1-0.2 wt %. The slurry effluent isdischarged from each polishing device 2 to the slurry effluentregeneration unit 6 through a discharge channel 13.

The slurry effluent regeneration unit 6 regenerates the slurry effluentby separating it into a regenerated and concentrated slurry fluid(hereafter simply referred to as regenerated slurry fluid) which isconcentrated to a given concentration which is the same as that of aninitial or original slurry fluid, and a permeate fluid. The regeneratedslurry fluid is fed from the slurry effluent regeneration unit 6 througha circulation channel 14 which merges with the feed channel 11 so as tobe circulated through the individual polishing devices 2. Intermediateits length, the circulation channel 14 has a branch connecting it to theslurry feeder 5. The regenerated slurry fluid is fed to each polishingdevice 2 by opening valves 15, 16 disposed in the circulation channel14, and is also fed to the slurry feeder 5 by opening a valve 17disposed in the branched channel. In the manner, by controlling theopening of the valves 15-17, the regenerated slurry fluid can beselectively fed to the polishing devices 2 and the slurry feeder 5. Thepermeate fluid is passed from the regeneration unit 6 to the slurryfeeder 5 through a permeate channel 18, where it is used to dilute thestock solution used to prepare the slurry fluid. Each of the valves 9,10, 12 and 15-17 is controlled by a controller, not shown.

FIG. 2 is a schematic diagram of the slurry effluent regeneration unit6, which comprises a crusher 21, a fluid quality regulator 22, aconcentration unit 23, a coarse filter 24, a back washer 25, aconcentrated fluid tank 26 and a permeate fluid tank 27.

The purpose of the crusher 21 is to crush agglomerations of abrasivegrains contained in the slurry effluent. A schematic diagram of thecrusher 21 is shown in FIG. 3. Specifically, the crusher 21 includes acrushing tank 32 having a crushing chamber 31 therein, and a mill 33, anagitator 34 and a ultrasonic vibrator plate 35 which are disposed withinthe crushing tank 32. A pressurizing circulation unit comprising acirculating pipe 36 and a pressurizing pump 37 is connected to thecrushing chamber 31. The ultrasonic vibrator plate 35 is connected withan ultrasonic oscillator 38 which energizes the plate 35 for vibrationat a high frequency. The combination of the vibrator plate 35 and theoscillator 38 defines an ultrasonic oscillation system.

The slurry effluent from the discharge channel 13 is initially injectedinto the mill 33 at a pouring port 39. The agglomerations of abrasivegrains contained in the slurry effluent are crushed by the mill 33, andare then further crushed and dispersed by the ultrasonic vibration ofthe vibrator plate 35, which is energized by the oscillator 38. Theslurry effluent which accumulates in the crushing chamber 31 is agitatedby the agitator 34. Injection of the slurry effluent into the crushingchamber 31 is via the pump 37 and through the circulating pipe 36, whichcauses an impingement of the slurry effluent against the internal wallof the crushing chamber 31, thus crushing the agglomerations intoindividual abrasive grains.

It is not always necessary to use all three of the mill 33, thepressurizing pump 37 and the ultrasonic oscillator 38, but any one ofthese three may be chosen as required. However, it is effective to use acombination of a pressurizing circulation crushing technique using thepressuring tank 37 and an ultrasonic oscillation crushing techniqueusing the ultrasonic oscillator 38. After the crushing step, the slurryeffluent is discharged from the crushing tank 32 through a dischargeport 40 into a channel 41 to a stock solution tank 42 (see FIG. 2) ofthe fluid quality regulator 22.

Referring to FIG. 2, the purpose of the fluid quality regulator 22 is toregulate the quality of the slurry effluent crushed by the crusher 21,and/or to perform a pretreatment, including a specific gravityadjustment and a pH adjustment, which enables an efficient concentratingoperation within the concentrating unit 23. The fluid quality regulator22 comprises a stock solution tank 42, an agitator 43, a desitometer 44,a pH meter 45, a specific gravity controller 46 and a pH controller 47.The pretreatment is performed while agitating the slurry effluent bymeans of the agitator 43. The combination of the desitometer 44 and thespecific gravity controller 46 defines a specific gravity regulatorwhile the combination of the pH meter 45 and the pH controller 47defines a pH regulator.

The adjustment of the specific gravity is performed using thedesitometer 44 and the gravity controller 46. The specific gravity ofthe slurry effluent within the stock solution tank 42 is measured by thedesitometer 44. The specific gravity controller 46 adjusts if thespecific gravity or concentration of the slurry effluent has reached agiven value on the basis of a measured value of the specific gravity. Ifthe measured value of the specific gravity does not reach the givenvalue, the specific gravity controller 46 controls the specific gravityof the slurry effluent by adding a fresh slurry fluid or regeneratedslurry fluid thereto. In this manner, the concentration of the slurryeffluent is adjusted so that a regenerated slurry fluid having a desiredconcentration may be obtained.

The adjustment of the pH value is performed using the pH meter 45 andthe pH controller 47. The pH value of the slurry effluent within thestock solution tank 42 is measured by the pH meter 45. The pH controller47 determines if the pH value of the slurry effluent has reached a givenvalue on the basis of the measured pH value. If the measured pH valuedoes not reach the given value, the pH controller 47 adjusts the pH ofthe slurry effluent by adding an alkali solution or an acid thereto. Theslurry effluent, as it is discharged from the polishing devices 2, has apH value of about 9. The pH controller 47 adjusts the pH value of theslurry effluent so that a slurry effluent having a pH value of about10.5 is obtained. When the pH value of the slurry effluent is adjustedin this manner, the agglomerations of abrasive grains which have not yetbeen crushed become likely to be disintegrated, thus improving thedispersibility of abrasive grains in the slurry effluent.

The concentration unit 23 comprises a pair of concentrating membraneunits 49, 50, a heat exchanger 52 which is used in controlling thedegree of concentration of the regenerated slurry fluid, a flow ratecontroller 63 and a flowmeter 71. The concentrating membrane units 49and 50 are connected to the stock solution tank 42 via a channel 48, inwhich a pump 51 and the heat exchanger 52, serving as a temperatureregulator, are disposed. The pump 51 feeds the slurry effluent from thestock solution tank 42 to the concentrating membrane units 49, 50through the channel 48. The heat exchanger 52 adjusts the temperature ofthe slurry effluent before it is fed to the concentrating membrane units49, 50. Two valves 53, 54 are disposed in the channel 48 to control theflow of the slurry effluent to the concentrating membrane units 49, 50.

Each of the concentrating membrane units 49, 50 separates the slurryeffluent, after the regulation of the fluid quality thereof, into aconcentrate fluid and a permeate fluid. The concentrate fluid is passedfrom the concentrating membrane units 49, 50 through channels 55, 56,respectively, to a pair of microfilters 57 where it is coarselyfiltered. After the coarse filtration, the concentrate fluid isdischarged to the concentrate fluid tank 26 through a discharge channel58. The microfilters 57 removes abrasive grains which have not beencrushed from the concentrate fluid. In this manner, any damage of thewafer by the concentrate fluid is prevented when the concentrate fluidwhich accumulates in the concentrate fluid tank 26 is used as theregenerated slurry fluid. The concentrate fluid fed to the tank 26 hassubstantially the same concentration as the concentration of the slurryfluid used in the polishing device 2. Accordingly, the concentrate fluidcan be directly used as the regenerated slurry fluid. One of the pair ofmicrofilters 57 can be selected by opening or closing valves 59-62associated with the respective microfilters 57. It will be noted thatthe flow rate controller 63 is disposed in the discharge channel 58 inorder to control the flow rate of the concentrate fluid.

The back washer 25 comprises a pair of back wash chambers 64, 65, a pairof control valves 74, 75 and a pair of gas purgers 76, 77. The purposeof the back washer 25 is to cleanse the concentrating membranes in theunits 49, 50 utilizing the permeate fluid. The pair of back washchambers 64, 65 each operate to receive and temporarily store thepermeate fluid from the respective concentrating membrane unit 49 or 50through channels 66, 67. Valves 68, 69 are disposed in the channels 66,67 at locations downstream of the back wash chambers 64, 65,respectively, and are closed when these chambers 64, 65 store thepermeate fluid. When the valves 68, 69 are opened, the permeate fluid ispassed through a discharge channel 70 to the permeate fluid tank 27.

The flow rate of the permeate fluid is measured by the flowmeter 71disposed in the discharge channel 70. The flow rate controller 63controls the flow rate of the permeate fluid, as measured by theflowmeter 71, using the heat exchanger 52. That is, when the temperatureof the slurry effluent rises, the speed of the slurry effluent passingthrough the concentrating membrane increases, while in the oppositeinstance, the speed of the slurry effluent decreases. Thus, the flowrate controller 63 controls the flow rate of the permeate fluid bycontrolling the temperature fluid using the heat exchanger 52, so thatthe flow rate is maintained at a given value. When the flow ratecontroller 63 fails to maintain the flow rate of the permeate fluid at agiven value, it determines that the concentrating membranes are to becleansed, and a back wash is performed. A combination of the heatexchanger 52, the flow rate controller 63 and the flowmeter 71 definesthe degree of concentration control.

The back wash chambers 64, 65 are connected via channels 72, 73 to gaspurgers 76, 77, respectively. Control valves 74, 75 are disposed in thechannels 72, 73, respectively, thereby allowing the gas purgers 76,77 tofeed a high pressure inert gas (such as nitrogen or argon, for example)into the back wash chambers 64, 65, respectively. The inert gas preventsoxidation of the permeate fluid. The gas which is fed into the back washchambers 64, 65 causes a back flow of the permeate fluid within the backwash chambers 64, 65 through the channels 66, 67, respectively, suchthat the permeate fluid is strongly ejected onto the concentratingmembranes in the units 49, 50, thus cleansing the concentratingmembranes. It will be noted that the concentrating membrane units 49, 50are connected to the stock solution tank 42 via the channels 55, 56 aswell as a channel 78. When back washing the concentrating membranes inthe units 49, 50, both of the valves 53, 54 disposed upstream of theunits 49, 50 and the valves 79, 80 disposed downstream of the units 49,50 are closed, while valves 81, 82 disposed in the return channel 78 areopened. In this manner, the permeate fluid used in the back wash processis returned to the stock solution tank 42 through the return channel 78.It is to be noted that the back wash process for cleansing the membranesin the units 49, 50 is performed separately for each unit.

The concentrate fluid in the concentrate fluid tank 26 is dischargedinto the circulating channel 14 and fed to the polishing devices 2 orthe slurry feeder 5. On the other hand, the permeate fluid from thepermeate fluid tank 27 is discharged through the channel 18 to theslurry feeder 5.

The operation of the plant 1 will now be described.

The slurry effluent which has been used in the polishing process in eachpolishing device 2 is transferred to the crushing chamber 31 of thecrusher 21. It is to be understood that agglomerations of abrasivegrains which have diameters on the order of about 500 nm are present inthe slurry effluent. It is also to be understood that abrasive grains ina fresh fluid have diameters of around 100 nm, and thus an agglomerationis formed of about 125 abrasive grains. It is possible that theagglomeration also contains fragments of films abraded from the waferand impurities such as exfoliation from the polishing pad. However, theamount of such fragments of films and impurities is negligible comparedwith the quantity of the abrasive grains.

The slurry effluent containing agglomerations of abrasive grains isintroduced into the crushing chamber 31 through the pouring port 39,shown in FIG. 3, and the agglomerations in the effluent are crushed bythe mill 33. After the crushing operation, any remaining agglomerationsof abrasive grains are subject to a crushing and dispersion effected bythe ultrasonic vibration of the ultrasonic vibrator plate 35. Inaddition, the slurry effluent which is pressurized by the pump 37 ispassed through the circulating pipe 36 and ejected into the crushingchamber 31, whereby the remaining agglomerations of abrasive grainscontained in the slurry effluent impinge upon the internal wall of thecrushing chamber 31 and are crushed.

The abrasive grains which are crushed in such manner are dispersedevenly throughout the slurry effluent in a floating condition as aresult of the agitating effect by the agitator 34, and are then passedthrough the discharge port 40 and the channel 41 and transferred intothe stock solution tank 42 shown in FIG. 2.

The desitometer 44 and the pH meter 45 measure the specific gravity andthe pH value of the slurry effluent in the stock solution tank 42, andthe specific gravity controller 46 and the pH controller 47 regulate thequality of the slurry effluent in accordance with such measurements.After the regulation of the fluid quality, the slurry effluent is pumpedby the pump 51 through the heat exchanger 52 to the respectiveconcentrating membrane units 49, 50.

The slurry effluent is separated into a permeate fluid and a concentratefluid by the concentrating membrane in each unit 49, 50. The concentratefluid is passed through the channels 55, 56 and fed to the microfilters57 where it is filtered coarsely. The filtered concentrate fluid passesthrough the flow rate controller 63 and the discharge channel 58 to theconcentrate fluid tank 26. On the other hand, the permeate fluid passesthrough the channels 66, 67 and is stored temporarily in the back washchambers 64, 65, and is subsequently transferred from the back washchambers 64, 65 to the permeate fluid tank 27 while the flow rate of thepermeate fluid is being measured by the flowmeter 71.

When using the permeate fluid which is temporarily stored in the backwash chamber 64 to cleanse the concentrating membrane in the unit 49,the valves 53, 79 are closed while the valve 81 is opened together withthe control valve 74, thus allowing the inert gas from the gas purger 76to be blown into the back wash chamber 64. The time interval duringwhich the inert gas is blown into the chamber 64 is chosen so that thepermeate fluid within the back wash chamber 64 is completely removed.The cleansing action of the concentrating membrane in the unit 50similarly is performed by blowing the inert gas from the gas purger 77into the back wash chamber 65. When the cleansing or back wash of theconcentrating membrane of one of the units 49, 50 is being effected, theconcentrating membrane of the other unit (50, 49) is used to continuethe concentrating operation. In this manner, the concentrating operationis continuously performed using the pair of concentrating membrane units49, 50 in an alternate fashion. It is also to be noted that there areprovided two microfilters 57. This allows for continuous operation ofthe plant 1 such that when one of the microfilters is being changed, theremaining microfilter may be used to continue the concentratingoperation.

The concentration of the concentrate fluid stored in the concentratefluid tank 26 is adjusted by changing the temperature of the slurryeffluent by means of the heat exchanger 52, which controls the speed atwhich the slurry effluent passes through the concentrate membrane in theunits 49, 50. When the temperature of the heat exchanger 52 is raised,which increases the speed of the slurry effluent, the concentration ofthe concentrate fluid is increased. On the other hand, the concentrationof the concentrate fluid is decreased when the temperature of the heatexchanger is controlled to reduce the flow speed of the slurry effluent.The flow speed is controlled by the flow rate controller 63 on the basisof the flow rate of the permeate fluid as measured by the flowmeter 71.

The permeate fluid stored in the permeate fluid tank 27 is fed to theslurry feeder 5, where it is used to dilute the stock solution used toprepare a fresh slurry fluid.

The abrasive effluent regeneration plant 1 of the present embodiment hasthe following advantages:

1. Agglomeration of abrasive grains contained in the slurry effluentwhich has been used to polish a semiconductor wafer are crushed duringthe crushing step and separated into a concentrate fluid and a permeatefluid, with the concentrate fluid being reused as a regenerated slurryfluid in polishing the semiconductor wafer. Accordingly, the amount ofpolishing stock solution used and the amount of sludge produced aresignificantly reduced. This reduces the manufacturing cost of asemiconductor device.

2. The crushing step allows a regenerated slurry fluid to be obtainedwhich has abrasive grains of grain diameters comparable to the singleabrasive grains in the fresh slurry fluid.

3. The use of the mill 33 enhances the effect of crushing theagglomerations of abrasive grains. A pressurizing circulation processenabled by the pressurizing tank 37 and/or ultrasonic oscillationprocess enabled by the ultrasonic oscillator 38 may be used incombination with the mill 33, thus allowing the agglomeration ofabrasive grains to be crushed in a reliable manner.

4. Since the concentration or the specific gravity of the slurryeffluent is adjusted, a concentrate fluid having a desired concentrationis obtained. The pH value of the slurry effluent is also adjusted, andaccordingly any remaining agglomerations of abrasive grains which werenot been crushed during the crushing step are easily disintegrated inthe process of being fed to the concentrating membrane units 49, 50,thus improving the dispersibility of the abrasive grains in the slurryeffluent.

5. An agitation of the slurry effluent by the agitator 34 allows thecrushed abrasive grains to be evenly dispersed throughout the fluid.

6. A coarse filtering of the concentrate fluid by the microfilter 57prevents damage of a semiconductor wafer from occurring as it ispolished using the regenerated slurry fluid.

7. The use of the permeate fluid in diluting the stock solution allows afresh slurry fluid to be obtained with an improved dispersibility ofabrasive grains. Temporary storage of the permeate fluid in the chambers64, 65 allows a back wash process of the concentrating membrane usingthe permeating fluid at the time when contamination of the concentratingmembrane is aggravated, thus allowing the concentrating membrane to becleansed in a simple manner using the permeate fluid.

8. The flow rate of the permeate fluid is detected by the flowmeter 71,and the temperature of the heat exchanger 52 is controlled by the flowrate controller 63 on the basis of the detected flow rate, whereby thespeed of flow of the slurry effluent before it is subject to theconcentrating operation can be controlled, allowing a concentrate fluidhaving a desired concentration to be obtained.

9. The provision of the pair of concentrating membrane units 49, 50 andthe pair of back wash chambers 64, 65 allows one of the concentratingmembrane units to be used even during the time the other unit 49 or 50is being cleansed, such that a continuous operation is enabled withoutrequiring an interruption of the slurry fluid regeneration operation.

10. The provision of the pair of microfilters 57 allows a continuousoperation by allowing one of the microfilters to be used while the othermicrofilter is being changed.

11. Since the concentration unit 23 is controlled such that aconcentrate fluid having the same concentration as the slurry fluidwhich is used in the polishing device 2 can be obtained, the concentratefluid can be directly used as the regenerated slurry fluid for thepolishing device 2.

12. A fully automatic regeneration and the circulation system can beconstructed since the concentrate fluid is fed to the polishing device 2through the circulation channel 14.

It should be apparent to those skilled in the art that the presentinvention may be embodied in many other specific forms without departingfrom the spirit or scope of the invention. Particularly it should beunderstood that the invention may be embodied in the following forms:

a) The crusher may include any combination of the mill 33, theultrasonic oscillation system 35, 38 and the pressurizing circulationsystem 36, 37. For example, the crusher may comprise the ultrasonicoscillation system and the pressurizing circulation system.

b) A dispersant may be used in the crushing step to promote crushingaction upon the agglomerations of abrasive grains.

c) The concentrating operation is not limited to the separation into aconcentrate fluid and a permeate fluid. By way of example, a concentratefluid may be produced by causing an evaporation of moisture in theslurry effluent. When the separation process is used, it may beimplemented by a centrifuging process, for example, rather than using aconcentrating membrane. In addition, the concentrate fluid may beobtained by removing a supernatant liquid after the separation byflocculation such as by precipitation.

d) A concentrate fluid having a higher concentration than that used inthe polishing device 2 may be produced. In this instance, the permeatefluid may be used in the slurry feeder 5 to dilute the concentratefluid, thereby preparing a regenerated slurry fluid.

e) A step of discarding the slurry effluent as a sludge by controllingabrasive grain diameters, when the number of reuses has increased toresult in abrasive grain diameters which are below a given value, may beused. In this instance, a high polishing capability of the slurry fluidis maintained.

f) The back wash process may be performed after a given number ofconcentrating operations. In such instance, the number of concentratingoperations is counted, and the back wash process is carried out when thecount reaches a given value. Alternatively, an operator may control thedegree of contamination of the concentrating membrane using a suitableinstrument, and may determine a timing when the membrane is to becleansed on the basis of a value obtained by the instrument, thusmanually effecting the back wash process.

g) One, two, three or more concentrating membrane units may be used.

h) One, two, three or more microfilters may be used.

i) The abrasive grains in the slurry fluid or polishing fluid are notlimited to alumina, but may comprise colloidal silicon or diamond.

j) The present invention may be implemented as a system for feeding theconcentrate fluid to the polishing device after the concentrate fluid inthe concentrate fluid tank is transferred to a feeding tank.

k) The present invention is not limited in its application to theregeneration of an effluent which has been used in the polishing stepfor a semiconductor wafer, but may also be used in the regeneration ofan effluent which has been used in the polishing of a package.

Therefore, the present examples and embodiment are to be considered asillustrative and not restrictive and the invention is not to be limitedto the details given herein, but may be modified within the scope andthe equivalence of the appended claims.

What is claimed is:
 1. A method of reuse of a slurry effluent containingagglomerations of abrasive grains which has been used in polishing stepin the manufacture of semiconductor, comprising the steps of: crushingthe agglomerations of abrasive grains contained in the slurry effluentin a crushing chamber, wherein the crushing step is performed using apressurizing circulation process, where the pressurizing circulationprocess crushes the agglomerations of abrasive grains by causing animpingement of a pressurized slurry effluent against an inner wall ofthe crushing chamber while circulating the slurry effluent; aftercrushing the agglomerations of abrasive grains, adjusting concentrationand pH of the slurry effluent by adding fresh slurry fluid orregenerated slurry fluid thereto; after adjusting the concentration andpH of the slurry effluent, concentrating the slurry effluent byseparating the slurry effluent into a concentrate fluid and a permeatefluid using a concentrating membrane; regenerating an abrasive fluidusing the concentrate fluid containing the crushed abrasive grains; andcleansing the concentrating membrane using the permeate fluid.
 2. Themethod according to claim 1, wherein the crushing step includesagitating the slurry effluent to cause the crushed abrasive grains to bedispersed in the slurry effluent.
 3. The method according to claim 1,wherein the concentrating step includes controlling the concentration ofthe concentrate fluid by adjusting the temperature of the slurryeffluent.
 4. The method according to claim 3, wherein the concentrationof the concentrate fluid is controlled to he substantially the same asthe concentration of a fresh slurry fluid.
 5. The method according toclaim 3, wherein the concentrating step is performed using a pluralityof concentrating membranes disposed in a plurality of concentratingpaths.
 6. The method according to claim 5, further comprising the stepof cleansing a plurality of concentrating membranes in a time offsetmanner using the permeate fluid.
 7. The method according to claim 1,wherein the cleansing step includes purging a gas into a storage chamberwhich temporarily stores the permeate fluid to cause the permeate fluidto be ejected toward the concentrating membrane, and wherein the gas isan inert gas which prevents oxidation of the permeate fluid.
 8. Themethod according to claim 1, further comprising the step of filteringthe concentrate fluid.
 9. The method according to claim 8, wherein thefiltering step is performed using a plurality of filters disposed in aplurality of filtering paths.
 10. The method according to claim 1,further comprising the step of preparing a fresh slurry fluid using thepermeate fluid.